Reenforced-concrete structure



W. S. HEWETT.

REENFORCED CONCRETE STRUCTURE.

APPLICATION FILED MAR. 5, 1921.

1,413,404. e te Apr. 18, 1922.

3 SHEETS-SHEET T- J: W W 5 fill/m4? William 5 Hewett WO Q W. S. HEWETT.

vREENFORCED CONCRETE STRUCTURE.

APPLICATION FILED MAR. 23. 1921.

Patented Apr. 18, 1922.

3 SHhETS SHEET 2.

A [nvevzfor William 5 hewet t W. S. HEWETT.

REENFORCED CONCRETE STRUCTURE. APPLICATION FILED MAIL-5, I921.

1,41 3,404. Patented Apr. 18, 1922.

3 SHEETS-SHEET 3.

\ [RI/KRZZOT' R A Williamifieweff UNITED STATES PATENT OFFICE.

WILLIAM S. HEWETT, 0F MINNEAPOLIS, MINNESOTA.

REEN'FORCED-CONCRETE STRUCTURE.

To all whom it may concern:

Be it known that I, WILLIAM S. Hnwm'r, a citizen of the United States, resident of Minneapolis, county of Hennepin, State of Minnesota, have invented certain new and useful Improvements in Reenforced-Concrete Structures, of which the following is a specification.

My invention relates to concrete structures wherein hydraulic or pneumatic pressure causes the walls of the structure to be put under tension. Such structures are usually provided with reinforcing rods to receive this tension but before the unit stress in the rods is reached, the tension will cause the concrete to crack, resulting in leaks.

- Waterproofing preparations are frequently kee used butfare not entirely effective and add considerably to the initial expense and upof the structure.

he object of my invention is to provide a reenforced concrete wall which will not I crack and.cause leaks when under tension.

A further object is to provide a structure wall in which a considerable saving can be effected in the thickness of the concrete wall and the amount of steel required for reinforcing. I

My invention consists in placing rods in the wall under an initial tension equal to or in excess of the workingload on the rods, whereby the inner portion of the wall will be under compression and high tensile stresses will have no effect on the wall.

In the accompanying drawings forming part of this specification,

Figure 1 is a front elevation of a concrete water tank embodying my invention,

Figure 2 is a vertical sectional view of the same,

Figure 3 is a horizontal sectional view of a portion of the tank wall,

Figure 4 is a vertical sectiOnal view of the same,

Figurefi is a horizontal sectional view, illuatrating another method of building the wal Figure 6 is a vertical sectional view of the same,

uprights and tension rods to permit convenient access to the tension rod tightening means.

Specification of Letters Patent. Patented Apr, 18 1922,

Application filed March 5,

1921. Serial No. 449,849.

In the drawing, I have shown aconventional form of water tower and tank embodying my invention. It will be understood, however, that I do not confine myself to this structure, as the invention is capable.

of use wherever it is desired to prevent cracking of the concrete under tension.

In the drawings, 2 represents a water tank supported by the tower 3. When this tank is filled with water, it is evident that the walls will be subjected to high tensile stresses increasing from the top to the bottom of the tank. Such structures are usually provided with rods embedded in the concrete to resist this tension. These rods are usually stressed when in use about 16,000 pounds per square inch of their area, but before thisunit stress is reached, the concrete will usually crack, causing leaks and allowing the water to seep through and the walls to eflloresce and present an unfinished unsightly appearance to the outside of the tank.

To obviate this difiiculty, I place the rods under an initial tension so that the inner portion of the walls of the tank will be under compression, and in doing this, I may emphliy the following method.

eferring to Figure 3, 4 represents the concrete wall and 5 beams arranged vertically at intervals in the concrete wall, and connected to horizontal struts 6 by suitable castings 7. The struts are connected with an upright post 8 by suitable means, such as castings 9. These struts and the vertical beams have suflicient strength to resist the forces caused by the initial stress set up in the rods 10, the number and size of the struts and the shape and size of the beams being determined by these stresses. When the beams 5 and the struts 6 have been assembled, the rods 10 are placed on the outside of the beams, the number and size and spacing of these rods being determined by the stresses caused by the water pressure in the tank. As shown in Figure 4, the rods are arranged comparatively near together at the bottom of the tank, the spacing between the rods gradually increasing in width from the bottom toward the top, commensurate with the decrease in the lateral pressure of the body of water in the tank. The rods 10 are made adjustable at suitable intervals by the insertion of turn buckles 11 and when the rods are assembled, these turn buckles are tightened until the initial stress in each rod is approximately equal to the Working provided in the usual way for the inner surface of the concrete wall and the outer surface thereof, the concrete being placed in the usual or any preferred manner enclosing therods 10, the turn buckle 11 and the vertical beams 5. The concrete is then allowed to set until its strength under compression exceeds the stresses caused by the initial tension in the rods 10, after which the struts 6, the post 8 and the castings 7 and 9 are removed and the recesses formed by the removal of the casting 7 are then filled with concrete to provide a smooth inner surface for the tank wall.

I have found that where the reinforcing rods are placed under tension in this way and the inner portion of the tank walls held under compression, .cracking of the wall and seepage of the water therethrough will be entirely avoided. v

In sheet 3, Figures 5 to 8, I have illustrated another method for placing the reinforcing rods under initial tension. The inner portion of this wall, lying within the circumference of the rods 10, is first molded by any convenient method, such as shown in Figure 6, in which 6* represents a suitable form, and after the concrete in this part of the wall has become sufficiently set 'to withstand the pressure caused by the initial stress of the rods 10, these rods are put in place and the outer portion of the wall formed in the usual manner, as by the use of form 6". In building the inner portion of the wall, angle bars 12 are arranged at suitable intervals vertically in the wall and provided with holes to receive the threaded ends 13 of the rods. Nuts'14 are provided for these threaded ends.

In molding the inner section of the wall, recesses 15 are preferably provided to allow room for the ends of the rods and the nuts thereon and permit the convenient tightening or turning up of these nuts. When the concrete in the inner wall section has become sufficiently set, the rods are tightened until the stress therein is approximately equal to the working stress. as described with reference to the rods in Figures 3 and 4. The inner wall or section of concrete will then be in compression and at no time can be subject to high tensile stresses sufficient to crack it and cause leaks.

I have found in the erection of a structure of this kind that considerable economy may be effected in the use of concrete and steel. Under the present practice, it is customary to design walls such as are herein described, of such thickness that the unit stress in tension will not exceed 100 pounds per tensile square inch upon the area of the concrete and much concrete is not safe, even under this stress. Concrete, however, stand high compression forces and will be safe under compression of 500 pounds per square inch of the area. Therefore, only one-fifth as much concrete would be necessary to resist the compression caused by the initial stress of the rods as would be required to bring the wall to a suflicient thickness to keep the tensile strength of the concrete below 100 pounds per square inch; A,

considerable saving may thus be effected in the use of concrete. The stress of the rods when they are once placed and subjected to an initial tension equal to their working stress will not change. As it is allowable to use amuch higher stress in the rod in which the stress does not change than it is in a rod in' which the stress is constantly changing, it would be allowable to use a much higher unit working stress in rods placed as described in my invention than it would be if placed in the ordinary manner. I am thus able to materially reduce the amount of steel necessary for a structure of this kind.

I make no claim in this application to any style or construction of building forms for molding concrete walls or for depositing the concrete, as structures of this kind may be erected'in various ways and still be within the scope of .my invention.

I claim as my invention:

1. A method of reinforcing enclosing concrete wall structures subject to radial stress which consists in arranging independent rods around a frame structure, putting each rod under an initial tension equal or approximately equal to the working stress to which the concrete is to be subjected, molding the concrete around the structure and the rods, then removing the frame structure.

2. A method of reinforcing concrete structures subjected to internal hydraulic or pneumatic pressure which consists in arranging circumferential reinforcements on a frame, putting the reinforcements under an initial tension equal or approximately equal to the working stress to which the concrete is to be subjected, moulding the concrete within the reinforcements then removing the frame.

3. A method of reinforcing con rete structures subjected to internal hydraulic or pneumatic pressure which consists in arranging circumferential reinforcements on a frame, putting the reinforcements under an initial tension equal or approximately equal to the working stress to which the concrete is to be subjected, moulding the concrete within and without the reinforcements, permitting the concrete to set, then removing the frame. In witness whereof, I have hereunto set my hand this 1st day of March 1921.

WILLIAM S. HEWETT.

will 

